1. Field of the Invention
The general inventive concept described herein is directed to image compensation and, particularly, image forming with compensation of a distorted image.
2. Description of the Related Art
Generally, an image forming apparatus, such as a multi function apparatus, a duplicator, a scanner, etc., includes a scanning part to scan an object to be copied and to generate image data of the scanned object. If the object to be copied is a book, opposite pages are opened and placed face-down on a scan plane to be copied. Since a central part of the book between the opposing pages is removed from the scan plane by a height determined by the binding area of the book, the amount of light reaching the central part is smaller than the amount of light reaching the part of the pages in contact with the scan plane. Consequently, in a scanned image, the central part of the opposing pages, in an area which will be referred to herein as a “folding area,” becomes darker than comparably formatted other parts in the image. FIG. 1 illustrates an example of the folding area 110.
The folding area 110 is a substantial distortion in the resulting image and it is therefore desirable to remove the folding area 110. Typically, to remove the folding area 110, a parameter is extracted by a histogram analysis of the input image data, and compensation of the distorted image data is performed based on the extracted parameter.
In conventional compensation, the histogram of the image data is analyzed to obtain the locations of sections where the pixel value of a foreground part and a pixel value of a background part are of a predetermined brightness, and then compensation is performed section-by-section in accordance with the brightness of the section being compensated. Since this compensation requires that the foreground part and the background part of the input image are consistently presented in the same colors, respectively, that is, the foreground part is always in one color and the background part is always in another color, such as when the input image is composed of dark characters on a light background, application of this compensation technique is limited. Also, if a book contains a picture, it is impossible by the traditional methods to distinguish a background value from a foreground value by the histogram analysis. Consequently, it is difficult to remove the folding area 110 through traditional distortion compensation of an image.